The femur bone (thigh bone) has peculiar shape and curvatures (anatomical profile) comprising of its Head (1), Neck (2), Greater Trochanter (3), Lesser trochanter (4) and Shaft (5). Head portion is like a ball composed of dense cancellous bone. Neck has front (anterior) surface (6), back (posterior) surface (7), lower (inferior) surface (8) and upper (superior) surface (9). Neck is not cylindrical in cut section but flat and narrow near posterior and inferior surface having dense good quality bone called as calcar (10) and broad at superior portion containing less dense bone near superior and anterior surface. Axis of centre of shaft (11) makes an angle with axis of centre of neck and head (12) which is known as “neck shaft angle” (13), which generally varies from 120° to 140°. Plane of center of shaft of femur (14) makes an angle with the plane of center of neck and head (15), which is known as “angle of ante version” (16), and which generally varies from 5° to 20°. Hollow shaft of femur with medullary canal (17) has “anterior curvature” (18). Front wall of medullary canal of shaft of femur is called anterior cortex (19), back wall is called posterior cortex (20), inner wall is called medial cortex (21) and outer wall is called lateral cortex (22). Head (1) articulates with socket-acetabulum (23) making the hip joint. Portion of femur bone comprising head (1), neck (2) and upper part of shaft(5) is called as “Proximal Femur”. In normal human, various muscles are attached to this part of bone, exerting force and reacting to ground reaction force in different directions and in different amplitudes in different stages of walking, and these loads are cyclic in nature. In intact femur bone these forces are transmitted from proximal femur to shaft of femur effectively.
Incidences of unstable proximal femur fractures in elderly people are very high world wide and management of these geriatric or aged patients has become a challenge. These geriatric patients with old age osteoporosis require early mobilization with assisted full weight bearing. In this situation it is essential that different forces acting on the femur should be transferred efficiently to the fracture fragments without displacement, leading to healing of fracture.
This demands implant assembly with proper biomechanical properties, such as:                The implant should acquire minimum area of the bone to provide anatomical reconstruction with stable biological (MINIMALLY INVASIVE) osteosynthesis (fixation of fractured bone fragments).        The funnel shaped femur medullary canal (17) makes an ante version angle (16) of around 5° to 20° with neck and head of femur bone and the femur shaft has anterior curvature (18). The implant must match completely with the above mentioned anatomic profile of femur bone to distribute the forces evenly like an intact bone.        At the same time implant should be capable to react effectively to large, dynamic (in magnitude and direction) and cyclic loads when patient starts walking bearing the weight on limb. Implant should allow gradual adaptation of the fractured bone fragments by allowing guided limited controlled collapse of gap between the fixed bone fragments leading to early bone to bone contact which results into faster healing.        Implant should be stable enough to provide rotational stability, so that during any rotational forces the implant and the comminuted bone should move as one unit.        Implant design and fixation must be such that it should provide early mobilization and should allow assisted full weight bearing.        The femur size and other related properties vary from person to person. Therefore, it is necessary to develop an implant assembly that would be suitable for any femur which meets the essential parameters. Along with these biomechanical properties, the implant unit should be easy to fix and should provide maximum accuracy of fixation, so that it is adoptable to average surgeon giving reproducible results.        
There are a variety of devices used to treat proximal femoral fractures. Fractures of the neck, head or intertrochanter of the femur have been successfully treated with a variety of Dynamic Hip Screw (DHS) assemblies as shown in FIG. 4, which generally include a compression plate (24) with a barrel member (25), a lag screw (26) and a compressing screw (27). The compression plate (24) is secured to the exterior of the femur-lateral cortex (22) and the barrel member (25) is inserted into a predrilled hole in the direction of the femoral head (1). The lag screw (26), which has a threaded end (28) and a smooth portion (29), is inserted through the barrel member (25), so that it extends across the break and into the femoral head. The threaded portion (28) engages the femoral head. The compressing screw (27) connects the lag screw (26) to the plate (24). By adjusting the tension of the compressing screw (27), the compression (reduction) of the fracture can be adjusted. The smooth portion (29) of the lag screw must be free to slide through the barrel member (25) to permit the adjustment of the compression screw. Compression screw assemblies are shown by the following patents: Pixel U.S. Pat. No. 4,432,358; Callender, Jr. U.S. Pat. No. 3,374,786; Pugh et al. U.S. Pat. No. 2,702,543; Griggs U.S. Pat. No. 4,530,355; Blosser, U.S. Pat. No. 3,094,120; and Wagner U.S. Pat. No. 3,842,825. The Blosser and Wagner patents illustrate the use of multiple screws to prevent rotation of the lag screw relative to the compression plate and barrel member. A surgical bone pin, which functions like a lag screw and compressing screw, but which doe's not include a compression plate is shown by Cochran et al. U.S. Pat. No. 3,103,926. These assemblies fail in unstable fractures due to various biomechanical problems.
Subtrochanteric and femoral shaft fractures have been treated with the help of intramedullary rods which are inserted into the marrow canal of the femur to immobilize the femur parts involved in fractures. A single angled locking screw is inserted through the femur and the proximal end of the intramedullary rod. In some varieties, one or two screws may also be inserted through the femoral shaft and through the distal end of the intramedullary rod. The standard intramedullary rods have been successfully employed in treating fractures in lower portions of the femoral shaft.
The Grosse-Kempf nail, manufactured by Howmedica Company of Rutherford, N.J., is believed to be one of the earliest intramedullary nailing devices introduced into the United States. The Grosse-Kempf nail includes a threaded hole in the intramedullary rod for receiving the interlocking screw. The fully threaded screw cannot slide through the threaded hole to permit the type of compression found in the compression screw assemblies discussed above. Furthermore, the axis of the threaded hole coincides with a line between the greater to lesser trochanter and not in the direction of the femoral neck.
The commercially available Kuntscher Y-nail includes a flanged cloverleaf shaped intramedullary nail which is inserted through a hole in a single femoral neck nail. The rod includes a longitudinal slit. The Kuntscher device is indicated only for unstable trochanteric fractures. Neither the Kuntscher device, nor the Zickel nail, includes distal anchoring means and both therefore are not useful for treating distal fractures. The femoral neck nail of the Kuntscher device, which is angled toward the femoral neck, is locked into place by the intramedullary rod. Thus, the Kuntscher Y-nail is also not indicated for femoral neck fractures.
The Russell-Taylor interlocking nail system, manufactured by Richards Medical Company of Memphis, Tenn., includes an intramedullary rod having two pairs of coaxial holes through its proximal end. The axes of the pairs of holes intersect to provide a left or right orientation for insertion of a single locking screw. The screw is designed to pass from the greater to the lesser trochanter. There is not sufficient mechanical support to allow usage of the locking screw in the direction towards the femoral head because the second pair of coaxial holes weakens the nail when loaded in that direction. Further, the locking screw is a fully threaded screw which does not permit sliding of the screw relative to the intramedullary rod. Another bone-nail which permits left-right orientation by means of ‘criss-cross’ nail holes is shown by Ender U.S. Pat. No. 4,475,545.
Current intramedullary compression hip screw systems also provide new limitations that hamper their effectiveness. One such limitation is evident in both Lawes' and Durham's designs. These designs require the use of a set screw to prevent rotation of the lag screw; the set screw in the Lawes patent interacts directly with the lag screw, while Durham's is indirect with the lag screw. To ensure proper mating takes place the Smith & Nephew Richards' systems provides a torque wrench, while Howmedica's Gamma Nail system requires tightening of the set screw to full engagement and then backing it off. Over time, loss of calibration of the torque wrench and improper engagement by the surgeon user could lead to an unsatisfactory engagement and decreased usefulness.
As shown in FIG. 5, Howmedica's Gamma Nail system comprises of unitary Gamma Nail (30) with mediolateral angle and has a large proximal diameter (36) and single large hole (71) for a single large transfixing Gamma hip screw (31). Nail's distal end (32) is straight, of short length and pluralities of distal locking screws (33) are in same plane as of proximal hole (71) in nail.
Recently available Synthes -AO PFN, PCT/CH/99/00581 Application Number and WO 01 39679 A1 International Publication Number has described intramedullary nail has provision of plurality of transfixing hip screws, one large screw inferiorly near narrow calcar and one small screw superiorly. Proximal diameter of nail is large and direction of proximal holes and distal holes are in same plane in nail and targeting device. In short length nail, distal end is straight without any anterior curvature, so it is same for right or left side of femur.
Modular nailing systems have two piece nail, one base member and other extension member as disclosed by Simpson et al in U.S. Pat. No. 5,122,141, and other modular nails, taught in prior art, have modular sleeves or inserts, proved to be biomechanically improper and technically very difficult to implant in human body by surgeon.
Mechanical and clinical studies undertaken by inventor have revealed technical problems and disadvantages with prior art.